full throttle holding back

gill vanderwerf

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Sep 9, 2019
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i have a problem that when i go full throttle ,y engine is holding back i have changed carburetors and moved the needle up and down to all positions but its still doing it and it seems to get worse .....the carburetors came with the kits i got should i maybe get a after market carb and if so what do i need i am running a 66/80 cc china motor right now.....please advise
 

gill vanderwerf

Active Member
Sep 9, 2019
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Gill, I have known guys with out of commission chain saws and weed eaters that became true believers.
Follow the instructions.
Tom
well i got a bottle and mixed it in my 2 galon gas can and i poured some in my tank...just a little bit and let the bike run on its own for 20 min will ride it tomorrow for a bit dont think ill see improvement right away guess that will take a tank or two..
 
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Greg58

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May 1, 2011
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If it's bogging at wide open the jet is too large, you'll need to check your plug color to see how the mixture is. The darker the porcelain the richer your mixture is, not talking about oil to fuel ratio, air to fuel ratio. Try this, remove the muffler end cap and do a test run if you can withstand the sound, if it runs better without the end cap the jet is too large. Without the end cap some of the raw fuel will be purged from the cylinder which will lean the air to fuel ratio.
 

mountain80

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Aug 8, 2008
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Pipe geometry and primary header length play a big part as well. I hit a wall at 6500 rpm than it can break through eventually and run to 8600 and beyond but it is not what I want...
 

Larry Trotter

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Nov 26, 2017
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Probably just running rich. Move the needle clip to the top and if it’s better than than on the bottom then get another smaller main jet like a 65 and try.
 

gill vanderwerf

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Sep 9, 2019
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okay i tried pretty much everything you all suggested only thing i did not do is order a new carburator or jets and get a new spark plug . would a better after market carburetor help..? if so what kind should i buy i run a 66/80 cc
 

Greg58

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May 1, 2011
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First is this a new engine? How many miles ? If it’s new I wouldn’t worry about it, if it will run 25-30 you need to put some time in riding till it’s broken in, after it loosens up the tuning needed could change.
 

Greg58

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May 1, 2011
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It may be time to buy a few jets and see if you can get it better, I’ve never bought jets so I’m no help, I solder and drill mine. Larry suggested a #65, that may help. It’s funny that jet number related to opening size is backwards from drill bits, confusing to all.
 
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gill vanderwerf

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Sep 9, 2019
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so i got a new spark plug the old one was dry as a bone and brown and i took my air filter off to see if it dont get enough air and i put my finger in fron of the intake and my hole finger got coated with gas/oil i think and insde the cap of the filter it was soaking wet......no i am really lost

and where can i buy a # 65 jet?
 

Larry Trotter

Active Member
Nov 26, 2017
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so i got a new spark plug the old one was dry as a bone and brown and i took my air filter off to see if it dont get enough air and i put my finger in fron of the intake and my hole finger got coated with gas/oil i think and insde the cap of the filter it was soaking wet......no i am really lost

and where can i buy a # 65 jet?
I have a 60 that I will never use that I will send you free. Put in the mail tomorrow and you will have it Tuesday I bet.